Regensburg 2007 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 35: SYBM Bioinspired Materials
MM 35.7: Vortrag
Donnerstag, 29. März 2007, 16:30–16:45, H16
Bamboo: Mechanical Optimisation and Efficiency — •Ulrike G.K. Wegst1 and Michael F. Ashby2 — 1Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart, Germany — 2Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ, UK
An optimised structure is one which uses the smallest quantity of the best material to perform its function, with adequate safety factor. Structural optimisation occurs not only in mechanical engineering, but also in nature: plants whose stems or stalks approach the optimum shape gain efficiency and a height advantage. Bamboo does this exceptionally. It provides the most efficient material for mechanical performance at minimum mass, supporting large loads due to self-weight and external forces. Bamboo achieves its efficiency in three ways: (i) by using efficient materials such as composites, (ii) by grading the structure, (iii) by shaping the component to form a tube. Investigated here is the material aspect of the structural optimisation of the orthotropic bamboo tube and the role which the microstructure plays in its mechanical performance. Concentrating on the elastic bending behaviour, the stiffness, strength and failure modes of bamboo are reviewed and algorithms and diagrams are proposed which allow the optimum property gradient and section shape to be selected. Man-made materials which exploit all three of bamboo's strategies for mechanical efficiency seem to be very rare. Given the ultimate structural efficiency that this combination allows, developing them in wood-based and other composites, for example, would appear to be worth serious consideration.